This invention relates to the field of bottle coating apparatus. More particularly, this invention relates to a machine and system for applying a UV curable strength enhancing coating to the bottoms and side walls of bottles and curing the coatings thus applied.
In the past several years there has been a significant and growing interest in increasing the strength of glass containers, especially bottles and jars, to improve pressure resistance and impact strength. This interest is particularly focussed on bottles intended to hold carbonated beverages, although bottles for noncarbonated products are also of interest. Increasing the pressure resistance strength and impact strength reduces the incidence of bottles bursting, whether under static load or impact load and/or it enables glass container manufacturers to save on material by achieving desired strength levels with thinner bottles.
In recent years several patents have been issued on coating materials for strength enhancement of glass containers. See, for example, U.S. Pat. No. 5,112,658 to Skutnik, and U.S. Pat. 4,891,241 to Hashimoto et al, the contents of which are incorporated herein. The coating materials of those patents are intended to be applied to glass containers as a thin liquid coating which is then cured by UV irradiation to increase the strength of the bottle, per se. This is to be distinguished from the field of burst containment coating where a relatively thick coating of material is applied to glass bottles to physically contain, i.e., prevent flying fragmentation, of the glass upon explosive rupture of the bottle. The coatings of the type of the Skutnik and Hashimoto patents increase the strength of the glass; burst containment coatings prevent the glass from flying about but do not increase the strength of the glass.
Strength enhancement coatings such as disclosed in the Skutnik and Hashimoto patents can be applied to the glass containers in a variety of ways, such as, e.g., by dip coating or spraying. However, dip coating and spraying each presents processing and/or environmental problems that are to be avoided if possible. Thus, the need exists for an effective, economical and practicable way to apply such coatings to glass containers and cure the coatings to produce strength enhanced glass containers on a commercial basis.
Coating and curing the bottom of the container presents different and more difficult problems from those encountered in coating the sides. Nevertheless, an effective way must be found to coat and cure the bottom of the container. Otherwise the strength of the bottom is not enhanced, and the objective of strength enhancement is seriously compromised.